AI 中文总结
介绍用算符形式主义和施温格 - 凯尔迪什路径积分研究开放系统，重点是开放有效场论和暴胀，以解决宇宙学中微观性质未知及引力系统相关问题，面向初次接触者。
AI 中文摘要
开放系统在物理学中无处不在。许多现实系统与环境自由度相互作用，其动力学与封闭系统不同。当微观描述未知时会采用开放有效描述。宇宙学的主要开放问题涉及微观性质未知的时空填充部分，引力系统常缺乏守恒能量概念且呈现非平衡动力学。这些讲义介绍研究开放系统的工具，重点是开放有效场论和暴胀，面向初次接触这些主题的学生和研究人员。
英文摘要
Open systems are ubiquitous in physics. Many realistic systems interact, at least weakly, with environmental degrees of freedom that may be too numerous, too complicated, inaccessible, or unknown. When only a subset of degrees of freedom is observed, its reduced dynamics can differ qualitatively from that of a closed system, displaying dissipation, noise, decoherence, memory effects, or loss of information into unobserved sectors. When the microscopic description is also unknown, one is led to an open effective description, in which the relevant degrees of freedom are treated systematically while the environment and the microscopics are parametrized rather than solved for explicitly. This perspective is especially important in gravity and cosmology. The main open problems of cosmology, including inflation, dark matter, and dark energy, involve spacetime-filling sectors whose microscopic nature is unknown and whose observed effects are primarily gravitational. At the same time, gravitational systems often lack a preferred notion of conserved energy because they are time dependent, and naturally display out-of-equilibrium dynamics. These lecture notes introduce the operator formalism and the Schwinger-Keldysh path-integral as tools to study open systems, with emphasis on open effective field theories and inflation. They are aimed at master students, PhD students, and researchers approaching these topics for the first time.
Comments140 pages, 8 figures
